Organic polysulfides containing two to five or even more sulfur atoms in the molecules have been found useful for many purposes such as additives for elastomers, antioxidants for lubricating oils, intermediates for the production of organic chemicals, insecticides, germicides and as an additive to diesel fuels to improve the octane number and ignition qualities of these fuels. These compounds have also been found useful in the compounding of extreme pressure lubricants and in the acceleration of rubber treating processes.
Such polysulfide compounds can be prepared by reacting mercaptans with elemental sulfur in the presence of a basic catalyst. For example, Biensan et al (U.S. Pat. No. 3,308,166) discloses that polysulfides can be prepared from a mercaptan and sulfur catalyzed by an amine using an alcohol promoter.
However, it has been shown that the polysulfide compounds cause metal corrosion partly due to the presence of polysulfide compounds having four or more sulfur atoms. A small quantity of these polysulfide compounds having four or more sulfur atoms are always present when a polysulfide compound having less than four sulfur atoms is prepared. Therefore, there is need to reduce the metal corrosiveness of the polysulfide compounds. It would also be a significant contribution to the art if a process were developed for reducing the metal corrosiveness of organic polysulfide compounds.